Servomotor system



July 38, 1950 R. D. M coY SERVOMOTOR SYSTEM Fiied May 10, 1945 3Sheets-Sheet 1 EECE/VE Q H W a INVENTOR QAWLEY D. MCCOY R. D. MycovsERvomo'rok SYSTEM 3 Sheets-Sheet 2 Filed May 10, 1945 INVENTOR IQQWLEYA2 mom-40 Qu uQ 3 Sheets-Sheet 3 INVENTOR R. D. M coY smavouo'ron SYSTEMJuly as, 195

Filed May 10,

Patented July 18, 1950 SERVOMOTOR SYSTEM Rawley D. McCoy, Bronxville, N.Y., assignor to The Sperry Corporation, a corporation of DelawareApplication May 10, 1945, Serial No. 593,049

25 Claims. (Cl. 318-144) My invention generally relates to a combinedradio and optical tracking system, and, more specifically, it relates toan electronic control circuit which is particularly adapted forcontrolling the operation of a servo motor for driving a target-trackingdevice in azimuth and in elevation under control of an error signalwhich may be derived from the radio circuits associated with the radiotracking device or from a manually controlled source of signal voltageused with the optical sight of the tracker. A radio and optical trackeror tracking device is designed so that the directivity axis thereof,whether a radio or optical axis, may be automatically or manuallycontrolled accurately to track a, target, such for err ample, as anaircraft and to determine the relative angular position of the target.

This application is a continuation-in-part of the pending application ofJoseph H. Lancor, Frederick R. Marindin and Rawley D. McCoy, Serial No.499,216, which was filed in the Patent Oflice on or about August 19,1943.

It is the primary object of the present invention to provide a servosystem comprising an improved electronic control circuit for controllingthe operation of a servo motor in which means are provided whereby torender the system operable in a stable manner smoothly to track atrelatively slow speeds and under varying load conditions.

More particularly, it is a primary object of the present invention toprovide a servo system in which one of the control signals is dependentupon the torque or upon some function of the torque exerted by the servomotor.

Another object resides in providing a servo system comprising agenerator controlled servo motor in which one of the control signals isproportional to the armatur current in said motor generator circuit.

Another object resides in providing a servo system including a generatorcontrolled motor, an electronic control circuit for controlling theoutput of the generator, and a feedback circuit for controlling theoutput of the circuit by means of which a signal proportional to motortorque is supplied in a regenerative fashion to the control circuit.

A further object resides in providing a system of the character lastabove referred to, in'which a signal proportional to torque rate issupplied in a degenerative fashion to said electronic control circuit.

A still further object resides in providing a 2 system of the characterlast above referred to in which a signal proportional to a timeintegration of the signal proportional to motor torque is supplied in aregenerative fashion to said control circuit; and still another objectof the present invention resides in providing such a servo system inwhich the output of the electronic control circuit and, in turn, theoutput of the generator is controlled by feedback signals includingsignal components proportional to torque, torque rate and torqueintegral, and also a signal proportional to servo motor rate as avelocity damping control voltage.

With the foregoing and other objects in view, my invention includes thenovel elements and the combinations and arrangements thereof describedbelow and illustrated in the accompanying drawings, in which:

Fig. 1 schematically represents a combined radio and optical trackerincluding the associated operative servos and control circuits therefor;

Fig. 2 is a wiring diagram illustrating one embodiment of the servomotor control circuit of the present invention; and

Fig. 3 is a wiring diagram of a modified form of control circuit.

As hereinabove indicated, the Present application constitutes acontinuation-inpart of pending application Serial No. 499,216 wherein isillustrated and described, and reference may be made thereto for afuller and more complete disclosure, a radio-optical tracker including aradio sight and an optical sight which are mounted to move together andsimultaneously in azimuth and elevation with their respectivedirectivity or sight axes substantially coincident or at least parallel.tional antenna and an indicator actuated by. circuits connected with thedirectional antenna so that the indicator will show the position of atarget relative to the directivity axis of the antenna. The indicator ofthe radio sight and the eyepiece for the optical sight are arrangedadjacent a control handwheel whereby the operator may optionally vieweither the indication of the target provided by the radio sight or usethe eyepiece of the optical sight in order to determine the direction inwhich the tracker should be moved to direct its directivity axis towardthe target.

Since the present application relates to a servo system including asignal voltage amplifier which is particularly adapted for providing Theradio sight includes a direc-v schematic nner one form of radio andoptical tracking ce which is equivalent to and functionsin"'-sirbstantially the same manner as the device shown in saidapplication Serial No. 499,216. Furthermore, since the control circuitsor signal voltage ampliflers for the elevation and azimuth servos may beidentical and in view of the fact that the present invention resides inthe electronic control, one servo, signal voltage amplifier andassociated sources of signal voltage are herein illustrated anddescribed.

In Fig. l, I indicates generally a scanner comprising aparabolicreflector I, which functions in conJunction with the antenna 3 totransmit radiant energy preferably in the form of a directional beam.The antenna 8 is employed both asa transmitting and receiving antenna,and is disposed substantially at the focus of the parabolic reflector.The reflector and its associated antenna are mounted for rotation abouta spin axis (1-41, the spin axis being assumed in the presentapplication to constitute the directivity axis of the scanner, a motor Iserving to rotate the parts about said spin .axis.

It is assumed for purposes .of explanation that the scanner is arrangedto provide conical scanning. That is, the transmitting antenna is eithermechanically or electrically displaced from the focus of the parabolicreflector, so that the axis of the transmitted beam describes a cone asthe scanner rotates about the spin axis a-a. Herein, it is assumed thatthis displacement is obtained by rotating the reflector slightly aboutthe axis H and locking it in displaced position, the axis of thereflector therefore will lie at a small angle with respect to the spinaxis a-apurposes of scanning with ultra high frequency energy, eitherthe transmitter or the receiver, or both, may have directionalcharacteristics, and in the present case it is assumed that the scannercomprises a transmitting and 'receiving antenna of a directionalcharacter;

A transmitter i of ultra high frequency energy, which ordinarily ismodulated with a short pulse, is connected through wave guide I to theradiator or transmitting antenna 3. Since the scanner iscontinuouslyrotated about its spin axis, the beam of radiated energy will describe acone about the spin axis H, and any target which appears within thescope of the cone so described min the 'path' of the transmitted energywill reflect energy to the antenna of the scanner. The energy soreceived is transmitted through wave guide t and through a T-R box Ito asuitable receiver. The T-R box may be of any desired construction andfunctions to reject signals of high intensity, such as those in theoutput of the transmitter, and to pass low intensity signals. Therefore,the reflected energy which is picked upby the receiving antenna and noenergy directly from the transmitter will be supplied to receiver 8.

The reflected radiant energy which is supplied to receiver I is in thenature of a voltage which is .a measure of the error angle or the anglebetween the directivity axis of the scanner and the direction therefromto the target. The receiver' 8 amplifies this error voltage and. sincethe scanner is operable or rotatable in two dimensions, azimuth andelevation, the amplified signal is resolved into its two azimuth andelevation error components, and these two components are employedrespectively to control the elevation and azimuth servos which serve toP0- 4- sition the directivity axis of the scanner in space. Hence, thesignal voltage output from receiver I is supplied through conductors toand lb to azimuth and elevation detectors or sensing circuits'lndicatedrespectively at I and II.

In conical scanning, the strength of the reflected or received energy,that is, the amplitude of the voltage of the received energy. dependsupon the position ofthe target or source of energy' relative to the axis'of the radio beam pattern. Since the beam pattern is rotating in aconical path, the reflected energy varies in strength as thebeam-pattern rotates. Thus, the envelope of; the reflected energy'wavereceived by the antenna varies in amplitude at a frequency correspondingto the spin frequency of the scanner andgthe amplitude of the'envelopedepends upon the amount. of displacement of the target-relative to thedirectivity axis, that is. the spinaxis of the'scanner in the presentdisclosure. It is to-be noted, furthermore, that the-phase relation ofthe variations in the envelope depends upon the direction of thedisplsgement of the target relative to the directivity a Therefore, theerror signal supplied to the receiver 8 is resolved into its twocomponents, elevation and azimuth error, by comparing the phase relationof each signal with respect to some reference phase. For this purpose, atwo-phase generator II is driven in synchronism with the spin motion ofthe scanner preferably by the motor 4, said generator comprisingwindings electrically displaced by Under these conditions, the generatordevelops voltages or reference voltages for resolving the error voltagesupplied for receiver 1 intoits azimuth and elevation components.Thesereference voltages may be considered at corresponding to azimuthand elevation components of the direction in which the axis of the beampattern is displaced relative to the directivity axis ,of the scanner atany instant. Such reference voltages are respectively supplied to theazimuth and elevation sensing circuits through conductors Ha, onevoltage being supplied to the azimuth sensing circuit and theotherthereof to the elevation sensing circuit.

The phase of the reference voltages supplied to the sensing circuits 9and II are respectively compared with the phase of the variations in theenvelope of the received or reflected energy. By efl'ecting a comparisonin this manner and separately with respect to what may be termed"elevation and azimuth referencevoltages," the azimuth and elevationcomponents of the measured displacement may be obtained. In other words,the magnitude of the azimuth and elevation error will be proportional tothe magnitude of the voltage supplied in the output of the azimuth andelevation sensing circuits.

These elevation and azimuth error voltages are employed respectively tocontrol the operation of the elevation and azimuth servo motors l2 and II. The voltage outputs of the elevation and azim'nth sensing circuitsare respectively supplied to si nal volta e amnliflers II and II, theconstructions of which will behereinafter speciflcally described. andthe outputs of these amplifiers serve to control the respectiveservo'motors.

The azimuth servo motor is arranged to move the scanner about a verticalaxis in azimuth in accordance with the azimuth error, while theelevation servo is designed to move the scanner about a horizontal axisto correct for elevation errors so that the directivity axis of thescanner may be placed in coincidence with the direction of a selectedtarget. As schematically illustrated in Fig. 1, the azimuth servo l2has. its output shaft 2l3 connected through gears 2l4, shaft 2 I5 andbevel gears It to shaft I! which, in turn, drives gear l8 meshing withgear I9 secured to the support 20 for the scanner. It will be understoodthat the support 20 is suitably mounted for rotation in azimuth andpreferably mounted to rotate about a vertical axis which lies coincidentwith the axis of wave guide 3. The parabolic reflector and antenna arepivotally supported as indicated at 2| on the support 20 for movementrelative thereto in elevation.

The elevation servo functions to rotate the scanner about its horizontalaxis 2i through the medium of its output shaft22 which is connectedthrough gears 23 to shaft 24, bevel gears 25 to shaft 26 and piniongears 21 which drive one input shaft 28 of a differential 29. The output30 of difierential 29 drives bevel gears 3|, shaft 32 and pinion gear 33which meshes with gear 34 mounted coaxially with the azimuth axis of thesupport or the wave guide 5. Gear 34 may be formed integral with gear 35or secured thereto in any desired manner, gear 35 meshing with gear 35and serving to drive shaft 31 to which is secured worm 38. Worm 38meshes with sector wheel 39 which is secured to the scanner and servesto rotate it in elevation about its horizontal axis 2|.

about its horizontal axis when the azimuth servo alone is caused tooperate. For this reason, the differential 29 is interposed in thetransmission between the elevation servo and gear 34. The second input40 to the differential is connected through gears 4| and with shaft l'l,which shaft constitutes one element of the transmission between theazimuth servo and the scanner support. The differential 29 is soarranged and the gear ratio so designed that when the azimuth servooperates to move the scanner in azimuth about its vertical axis, theazimuth servo will drive the input 40 to the difl'erential, therebycausing gears 34 and 35 to rotate in synchronism with the support 20.Therefore, when the azimuth servo alone operates to drive the scanner inazimuth, azimuth motion only of the scanner will result, and no verticalmotion or motion thereof in elevation about its horizontal axis 2| willbe imparted thereto.

From the foregoing, it should be understood that the error voltageswhich are derived from the scanner and which are measures of the angulardisplacement between the directivity axis of the scanner and thedirection toward a selected target, serve respectively to control theazimuth and elevation servos to move the scanner in a direction tendingto zero the errors. In order that the azimuth servo, when controlled bythe azimuth error voltage component derived from the scanner, shall havesubstantially the same response under all operating conditions of thescanner or shall not be comparatively loose or sluggish" in responseunder some conditions and unstable or jittery under other conditions, acorrection is introduced in the servo system so that the response of theservo will be substantially the same for all positions of the scanner inelevation. The true output value of the azimuth servo is measured in ahorizontal plane. If

the directivity axis of the scanner lies horizontally, the errormeasured thereby will be a true measure of error in a horizontal plane.Obviously, if the scanner measures the error in a slant plane, a signalwhich is inaccurate in magnitude will be supplied to control the azimuthservo, and the sensitivity of the error measuring means will varysubstantially as an inverse function of the secant of the angle ofelevation of the directivity axis of the scanner. In order to correctfor this undesired variation in sensitivity, the voltage output of theazimuth sensing circuit 9 is applied across a secant potentiometer 43and resistor 44 which is connected in series with the potentiometer andto ground. The secant potentiometer, of course, comprises a resistor sowound that the voltage output obtained therefrom by means of a 'wiper-vari es approximately as the secant of the angle the wiper is turnedthrough, and varies between some fractional part of the voltageimpressed across the potentiometer and series resistor and its fullvalue. In other words, the position of the wiper being a measure of anangle, the voltage picked off the potentiometer will equal the productof the voltage impressed across resistor 44 and the secant function ofthe elevation angle. The wiper arm 45 of the potentiometer is driven bymeans of worm wheel 46 which, in turn, is driven by worm 41 mounted torotate with shaft 26. The, position of wiper 45 will therefore dependupon the angle of elevation of the directivity axis of the scanner, andfor zero elevation angle the wiper will occupy the position illustratedin Fig. 1. As the scanner is rotated in elevation, wiper arm 45 willrotate along the secant potentiometer until the upper limit or theopposite end of potentiometer is reached corresponding preferably to anelevation angle of Since the secant of an angle approaches infinity asthe angle approaches a practical range extends from zero degrees toabout 80. The wiper 45 is electrically connected through conductor 45ato the azimuth amplifier as hereinbefore indicated. In comparison, ofcourse, the elevation sensing circuit I0 is connected directly with theelevation amplifier through conductor Illa.

As hereinbefore indicated, the servo motor control circuit of thepresent invention is designed and arranged to control the servo motorsunder automatic and manual tracking conditions. I have hereinabovedescribed one form of auto-' matic tracking device, and in the followingwill describe the optical system associated therewith. Mounted on thesupport 20 is an optical sight 48 which comprises an eyepiece 49arranged with its axis coincident with the axis about which it issupported to rotatein elevation relative to the support 20. The sight 48is secured to and rotated by a toothed sector 50 which is rotatablysupported on the support 20 and driven by a worm 5| mounted on shaft 31hereinbefore described. With this arrangement, the optical axis b'b ofthe object lens of sight 48 lies at'all times substantially parallelwith the directivity axis a--a of the scanner, and both of these axesare moved in elevation in synchronism. The operator may visually directthe scanner toward a selected target since the axes of the optical andradio sight are substantially coincident for distant targets, andthereafter the scanner may serve automatically to maintain thisdirectivity axis substantially on the target. Either automatic radarcontrol or manual control using the optical sight may be employed intracking the target with the device hereinabove described. 7

The handwheel 52, mounted on the support III, is manually operable inconjunction with either the radio or the optical sight to control one ofthe servo motors, as for example, the azimuth serve as herein shown anddescribed. A second handwheel, not illustrated, and which may beoperated in conjunction with a second sight, also not hereinillustrated, may be employed in controlling the other or elevationservo. Ordinarily, two operators are'employed to control the scanningdevice herein shown. The details of the control operated by thehandwheel 52 is shown in Fig. 2 and will be hereinafter described.However, in connection with Fig. 1, it will be observed that the signalvoltage output of the signal-producing device 53, controlled by thehandwheel 52,

a first remote sighting station in a manner similar to that in which thecontact II of switch 64' are indicated at l5 and I6 in Fig. 2. Theresistis supplied through conductor 53a through switch 54 to the azimuthamplifier. In Fig. 1, I have illustrated a simple form of switch 54which may be operated to connect the manual control system, or,alternatively, the radio control system in circuit with the azimuthamplifier. However, in Figs. 2 and 3, I have illustrated preferredarrangements whereby manual or automatic control of the servos may beeffected at the discretion of the operator. In either case, of course,.the servos are controlled through the signal voltage amplifiers l4 orl5 by means of an error signal voltage.

The present invention specifically relates to the servo motor controlcircuit which is designed to amplify the error signal voltage derivedeither from the scanner or from the handwheel-operated devices and tomix therewith other signals which are generated and connected to theamplifier in the manners hereinafter described so that servo motors willhave operating characteristics particularly adapting them for use withautomatic and manual tracking.

As shown in Fig. 2, the error signal voltage which is derived intheazimuth sensing circuit from the error voltage supplied to the outputof the receiver, may be supplied to the amplifier, or, the error voltagemay be derived from the handwheel-operated, signal-supplying deviceindicated generally at 53. In, Fig. 2, only sufiicient radar equipmentand associated circuits are shown asto provide a schematicrepresentation of the path traversed by the signal voltages from theantenna to the input of the amplifier, and the various parts andcircuits thereof bear the same reference characters as the correspondingparts and circuits illustrated in Fig. 1. In Fig. 2, the wiper 45 of thesecant wound potentiometer is connected through conductor 45a and choke55 to the contact arm 56 of switch 51, one terminal of which is open andthe other terminal 56 of which is electrically connected with thecontact arm 56 of a second switch 60. As indicated, these two switchesare adapted to be operated jointly so that when the arm '56 of switch 51engages the open contact, the arm 59 of switch 66 engages contact 6|which is connected through conductor 62 to the contact arm 63 of anotherswitch 64. One contact 65 of switch 64 is connected through conductor 66to the output of signal voltage-supplying device 53 which is controlledby the handwheel 52. The switch arm 59 of switch 60 is connected throughconductor 61 to one contact 66 of a switch 69, the contact arm III ofwhich is connected to the input of the amplifier l4. The other contact Hof switch 69 is connected through conductor 12 to the signal voltagegenerator of (ill ance-condenser network connecting thev switches 51'and 60 will be hereinafter described and the purpose. thereof fully setforth. It is obvious from an examination Of Fig. 2 that it all of theswitch blades of the switches occupy the full-line positionsthereinillustrated, a control signal voltage from the radar system will besupplied to the input of the amplifier l4. If switches 51 and ll besimultaneously operated to the dotted line posi tions, the radar systemwill be disconnected from the amplifier and the signal-supplying device58, operated by handwheel 52, will be connected to the input ofamplifier l4. With the switches 51 and 60 in the position lastdescribed, the signal from the device 53 may be interrupted and theremote sighting station 15 operatively connected with the amplifier bythrowing switch arm 66 to the dotted line position. Furthermore, theswitch arm 10 of switch 69 may be operated to the dotted line positionto interrupt the circuit from either the remote station 15 or the device53, and to connect the input of the amplifier with the remote station'16. Hence, the group of switches shown in Fig. 2 serve to affordselective connection of the amplifier with any sighting station or typeof sighting device, whether optical or radar.

For exemplary purposes, I have shown the device 53, which is actuated bythe handwheel II, in more or less schematic detail, in order to teachone manner in which the operation of the servos may be manuallycontrolled. The device 58, gen erally speaking, comprises a pair ofpotentiometers TI and I6 and a permanent magnet generator 19 which areall actuated by the handwheel 52.

It has been found in'practlce that an operator may more accurately andeasily track atarget when the control which he operates provides anaided tracking type of control over the servo. An aided tracking controlis effected when the control handle, for example, is positionable notonly to provide a signal which controls the rate of operation of theservo, but which also supplies a signal which is proportional to therate of displacement of the control and which provides a proportionaldisplacement in the output of the servos which greatly aids insynchronizing the tracker with the target. For distance targets whichhave relatively low angular velocities, tracking may best beaccomplished with apparatus providing either pure displacement trackingor a high ratio of displacement to rate tracking. When the target, isrelatively near and has high angular velocities, it is then desirable toprovide a relatively greater amount of rate tracking, or, to decreasethe ratio of displacement to rate tracking. The manual control hereinshown provides an electrical, variable ratio aided tracking systeminwhich the ratio of displacement to rate tracking ofthe aided trackingsystem decreases as the operator displaces the handwheel from itscentral or neutral position.

The servo motors, of course, drive the tracker at a rate dependent uponthe voltage of the,

tracking signal or the signal derived from the device 53, the ratetracking component of the voltage is dependent upon the displacement ofthe handwheel or is derived from the potentiometer 'I'I while thedisplacement tracking voltage component is proportional to the rateofmovement of the handwheel and is derived from the generator I8. Theratio of these voltages is controlled by the secondary potentiometer I8;

Potentiometer I1 is connected across a suitable source of D. 0. supplyand its wiper 88, which is connected through .conductor 8| in serieswith generator 19, is carried by shaft 82. This shaft is driven from thehandwheel 52 through a gear box 83 and a magnetic clutch 84. Generator'3 9 is similarly driven from the gear box 83 and the gearing thereinproportions the relative rates or displacements of the shaft 82 and thearmature of generator 19 for a predetermined angular rotation ordisplacement of the handwheel 52. Movement of shaft 82 in a clockwise orcounterclockwise direction will determine the polarity sense of thesignal voltage derived from the potentiometer 'Il while the angulardisplacement thereof moving the wiper 88 from a position substantiallymidway between the ends of the potentiometer resistor will determine themagnitude of the voltage. The servo controlled thereby will provide arate output proportional to the voltage derived from the potentiometer11.

As the handwheel is operated in one direction or the other, generator I9will supply a voltage output which is proportional to the rate ofmovement of the handwheel. The voltages from the potentiometer TI andfrom generator 19 will be combined in the input to the amplifiercontrolling the servo and that voltage component which is derived fromthe generator will result in a displacement of the servo outputproviding electrical aided tracking.

In order to control the ratio of rate signal to aided tracking ordisplacement signal, the second potentiometer I8 is provided, the wiper85 of which is also controlled by shaft 82 in the same manner as wiper88. As the wiper 88 is displaced from its neutral position, the voltageoutput is comparatively low and as the slider is further displaced, thisvoltage normally increases, but since resistance of the loadpotentiometer I8 also increases with movement of the wiper 85therealong, the wipers 88 and 85 being electrically connected, thevoltage drop across potentiometer I1 is reduced in a non-linear fashion.Thus, the voltage output of potentiometer I! will increase in anon-linear fashion as the wiper 88 is displaced from its central orneutral position.

Magnetic clutch 84 is connected through a switch 86 with the D. C. powersupply, above referred to, and when energized is designed to connectshaft 82 with the output of gear box 83. Switch 86 is preferablydesigned to be automatically opened when the controller 53 isdisconnected and some other controller is employed, deenergizing themagnetic clutch and allowing shaft 82 under the influence ofthecentralizing device indicated schematically at 81 to return thewipers 88 and 85 to a central or neutral position with respect to theresistors of the poten tiometers TI and I8.

The manual control of the scanner which entails an operation of thehandwheel 52 to control one of the servos, such as the azimuth servo,and another to control the elevation servo, may be accomplished inconjunction with optical sight 98. Additionally. this control may beemployed in connection with a scope or cathode ray tube,

one of which is indicated generally at 81. The scope or indicator 8! isconnected to receive a voltage from the output of the azimuth sensingcircuit (another may be connected across the output oi the elevationsensing circuit) and is adapted to provide on its screen an indicationof the: azimuth displacement of the directivity axis of the radioscanner, such as axis a-a. or of axis b-b of the optical sight relativeto the direction therefrom to a preselected target. Hence, the operatormay use either the scope in connection with the radio tracker to providehim with a visual indication in controlling the tracker to track atarget or he may employ the optical sights. In either case, the controlis the same.

The signal error voltages derived from the radio system and appearingacross the output of the sensing circuits or the voltages derived fromthe device 53 or the devices I5 or I6, as selected by the operator,which constitute azimuth and elevation control voltages, arerespectively employed to control the azimuth and elevation servos. Ihave herein shown the various controls for providing an azimuth signalvoltage and disclosed the azimuth servo amplifier for the purpose ofillustration, it being understood that a similar arrangement will beprovided to control the elevation servo.

Whichever controller is employed, its voltage output is supplied throughconductor 88 to grid 89 01' tube 98. The plate 9| and screen grid 92 oftube 98 are connected to a suitable power supply as indicated. Theoutput of tube 98 will appear as an amplified voltage across the loadresistor 93. Tube 94 has its plate connected through load resistor 95 tothe source of positive supp above referred to, and similarly its screen98 is connected with the screen grid of tube 98. When a signal isapplied to grid 89 of tube 98 an amplified signal of opposite phaseappears across resistor 93 and is supplied through lead 9'! to the grid98 of tube 99. The variation in current through tube 98 caused by thesignal on its grid varies the drop across cathode resistor I88 which, inturn, changes the bias of tube 94, producing an amplified voltage acrossload resistor 95 which is of the same phase as the signal applied to thegrid 89 of tube 98. 'The phase of the voltage across load resistor 95 istherefore opposite to that of the voltage on lead 91 and is-supplied bylead IM to the grid I82 0 tube I83.

The balanced output of the first stage of the amplifier comprising thetubes 98 and 94 varies the current in tubes 99 and I83 comprised in thesecond stage of the amplifier, the current variation being dependentupon the polarity and magnitude of the tracking signal voltage appearingon lead 88 or across the input of the amplifier. The cathodes of tubes99 and I83 are connected together and through a suitable cathoderesistor to ground in the conventional manner, while the screen grids ofthese two tubes are similarly connected in the usual manner to a sourceof suitable positive potential. The plates of tubes 99 and I83 areconnected through opposite halves I84 and I of the field winding ofgenerator I86 to a source of positive potential as shown. Condensers I81and I88 are preferably connected respectively across the two halves ofgenerator field windings. These condensers are employed to preventoscillations in the amplifier which may arise by virtue of its high gainand,

- 11 i also, these condensers serve to by-pass alternating voltagecomponents in the output of the The generator I is driven by a suitablemotor Ill preferably of the constant speed type. The field of thegenerator windings I and Ill will be controlled by'the signal voltagesupplied to the amplifier, the generator field having a direction andmagnitude which is dependent upon the polarity sense of the controlsignal voltage and its magnitude. The output voltage of the generator istherefore dependent upon the signal voltage applied to the amplifier andthe output of generator I" is connected, through leads III and III tothe armature oi a servo motor II2, corresponding for example to servomotor I2 in Fig. 1. preferably having a constantly excited or 'fixedfield as indicated, the field of motor II2 being preferably energizedfrom a suitable D. C. source. Under these conditions. the armature ofmotor H2 will be driven at a rate dependent upon the voltage appliedacross its terminals. Hence. since the rate of" motor H2 is dependentupon the voltage output of generator I which, in turn, is dependent uponthe signal voltage applied to the amplifier I4, motor III will drive ina direction and at a rate depending upon the polarity and magnitude ofthe tracking error voltage signal applied to the input of amplifier I4.As shown, the armature of motor II2 drives'shaft II! to which gear I issecured and which mahes with gear III.

The schematic showing of motor I I2 and its associated driving mechanismfor rotating gear III is representative of the corresponding arrangementof Fig. 1. That is to say, servo motor II2 corresponds to the azimuthservo I2 while gear Illcorresponds to gear It of Fig. 1, the shaft I IIand gear Ill'corresponding to the shafting and gears 2Il2I5 and I8through I8. It will, of course, be understood that any suitable form ofamplifier may be substituted for that described in the above.

For stabilization purposes, a voltage proportional to the rate or outputvelocity of the servo motor III is generated by a permanent magnetgenerator IIG which, as schematically shown, is

connected through shaft I II with the servo motor II2. The voltagegenerated by generator II is supplied through lead III to the controlgrid of tube I4. The polarity of this rate voltage is selected so thatit will act in a degenerative sense in the amplifier. An amplifiedvoltage .will ap pear across load resistor II which corresponds to thevoltage applied to the control grid of tube 94, and variations in thecurrent in tube 94 due to the voltage applied to its control grid causechanges in the voltage drop across resistor IIIII thereby changing thebias of tube ll, causing a correspondingly amplified voltage to appearacross load resistor 02.

The amplifier, as hereinabove described, pro-. duces balanced outputvoltages across load resistors I2 and I which comprise componentscorresponding to the tracking signal voltage in-.

put to-the amplifier and also to the velocity or output rate of theservo motor II2. An inverse feedback of a speed or rate voltage as abovedescribed is sometimes termed velocity damping, in

t it functions to oppose changes in the speed of'the servo motor. i 1

Although velocity damping voltages tend to stabilise the operation of avariable speed servo, they introduce other factors which tend towardinstability. It is well known that an inverse feedback system willoscillate at a frequency when the phase shift is at least and the gainis greater than unity, whereupon the feedback becomes regenerativerather than degenerative. One solution to avoid this dimculty is toprovide a means for attenuating the gain of the servo system in the zoneor frequencies where oscillations may occur. In accordance with thepresent invention, I propose to effect this attenuation by introducing aseconddegenerative signal into the amplifier, which signal depends uponthe rate of change of the torque exerted by the motor. arrangement tendsto oppose changes in the motor torque and hence substantially toattenuate'the gain of the circuit or servo system in those sistor IIIprovides avoltage proportional to the torque developed by the motor II2. The resistor I II is preferably small in comparison with theresistance of .the armatures of generator I It and motor I I2 in orderto avoid an undesirable voltage a drop in the circuit.

The voltage appearing across resistor Ill is connected through leads I20and I2I across the series resistance circuit comprising resistor I22 andI23, resistor I22 having a sliding contact I24 which is connected toground as indicated,

Therefore, the voltage on leads I20 and HI will be of opposite polaritywith respect to ground, but both voltages are dependentupon the torqueof the motor I I2 and the ratio of these two voltages is determined bythe position of the sliding contactl24 relative to resistor I22. Theprimary purpose of arranging the series resistor circuit in the mannerabove describedis for the purpose of obtaining a derivative and anintegration voltage component as will hereinafter be particularlypointed out.

Conductor 'I2l is connected through a resistor I" to conductor I26 whichserves to connect the RC. network, indicated generally at I21 andadapted to provide both derivative and integration voltage components,with the permanent magnet generator III. Conductor III is also ignnectedto conductor I20 through a condenser The voltage on conductor I2I, thatis, the voltage across resistor I21 and a part of I22, is differentiatedin the resistance-condenser network I21, by condenser I20 supplying avoltage across resistor I25 which is proportional to a first timederivative of the voltage proportional to motor torque. The voltageacross the other portion of resistor I22 is applied through resistanceI25 to condenser I28 and the voltage across this-condenser or thepotential to which it is charged will be proportional to. a timeintegral of the voltage proportional to motor torque. As is evident fromthe wiring diagram of Fig. 2, these voltages are supplied in oppositepolarity sense and in series with the speed generator II to theamplifier Id.

The first derivative voltage appearing in the output of the network I21,as above described, is connected in series with the velocity dampingvoltage derived from generator H6 and fed back in a degenerative sensethrough lead Ill to the amplifier I4. The degenerative or inversefeedback of a voltage which is dependent upon the torque rate of a motoror rate of change of torque developed by the servo II2 attenuates thegain of the amplifier circuit at the frequency at which the servo tendsto oscillate, or, at the frequency at which the phase shift would be 180and the inverse feedback circuit would become aregenerative feedbackcircuit.

One difficulty encountered with this type of electrical, variable speeddrive mechanism lies in the fact that the speed regulation of the motoris poor at low speeds. When the torque is increased at low speeds, thespeed of the motor is reduced due to the voltage drops in the armaturecircuits of the motor and generator as well as the effects of armaturereaction together with other losses. Obviously, in tracking systems ofthe character herein described, it is desirable that the speed output ofthe servo motor be primarily dependent upon the control signal voltagesupplied to the amplifier and substantially independent of the load onthe motor or the torque exerted thereby;

Heretofore, it has been proposed to provide the motor or generator of amotor generator system with compound fields. The use of a system ofappearing between the conductor ground. The torque or torque integralvoltage serves to improve the operation of the servo motor at slowspeeds and to provide an output rate this character in tracking systemsis not desirable because of the necessity of over compounding thefields, thereby rendering the systems unstable. It has also beenproposed to utilize the voltage across the armature of the motor andgenerator having components including the generated voltage and the dropin the armature windings as a regenerative feedback voltage whereby toincrease the field strength of the generator with an increase in motortorque. However, such a voltage, taken across the armatures of the motorand generator, contain spurious voltage components from the commutatorwhich must be filtered in order to provide a satisfactory and usefulvoltage which is dependent upon motor torque. Furthermore, a filter forthis purpose would necessarily have a long-time constant in order toblock the undesired spurious and higher frequency signals and, ofcourse, such a filter must necessarily reduce the sensitivity orresponse rate of the control circuit which is also very undesirable.

According y, in the present invention, a portion of the voltage acrossresistor H9, which is proportional to motor torque, is suppliedin aregenerative feedback fashion to the amplifier I4, whereby to increasethe field strength of the generator I06 as the torque developed by motorII2 increases. This is accomplished in the following manner. The voltagebetween lead I20 and ground is proportional to the torque of the motor,and when the torque is constant this voltage will be added in serieswith the voltage generated by generator H6 and fed back regenerativelyto the amplifier I4.

Since the conductors I20 and I2I are of opposite polarity with respectto ground, they may be connected through the RC network I21 to theconductor I26, as shown, to provide a torque feedback voltage which issupplied in a regenerative fashion to the amplifier and a torque ratevoltage which is supplied in a degenerative fashion through the commonfeedback circuit to the amplifier. Only a relatively small regenerativetorque voltage is necessary to maintain the desired speed regulatio ofthe motor at slow speeds and. therefore the position of the contact I24which is connected with ground is selected to which is principallydependent upon the input control signal voltage and which issubstantially independent of the load on the servo motor or the torqueexerted thereby. 0n the other hand, the voltage produced by the RCnetwork I21 which is proportional to a first time derivative of thetorque voltage or to rate of change of torque is employed in adegenerative fashion as compared to the regenerative feedback of thetorque signal voltage, and serves to permit of much greater gain in thefeedback loop including the permanent magnet D. C. generator IIB,thereby greatly improving the over-all operation of the servo system.The degenerative torque rate may also be considered as arate of changeof acceleration lag. Furthermore, the torque integration provided by theRC network I21 supplies a voltage output which is used in a regenerativefashion and serves to provide a more stable operation of the servo.

As hereinbefore indicated, the signal voltage between conductor I20 andground will be applied across resistor I25 and condenser I20 which is inseries therewith. Since the conductor I26 is connected to the resistanceI25 and condenser I 28 and at a point therebetween, an integrationvoltage component will be derived from the condenser I28 to function inthe regenerative manner above described.

Also, as hereinbefore indicated, the switches 51 and 60 for controllingan automatic or manual operation of the tracking device has connectedbetween the contact 58 of switch '51 and the switch arm 59 of switch 60,a resistance I29, contact 58 being connected through condenser I30 toground and switch arm 59 beingconnected through resistance I3I andseries connected condenser I 32 to ground. This network functions tohold over the signal voltage when switching from manual control toautomatic or vice versa, so that during the brief switching interval thesignal voltage may persist, in the input to amplifier I4 and theresultant continuous operation of the motor will maintain the radio andoptical axes on the target. In other words, this network insures smoothtracking during the switching transition period.

In Fig. 3, I have illustrated a modified form of control amplifier whichis adapted to control a servo motor in accordance with a radio derivedsignal or a signal from a manually controlled device. The control termshereinbefore described for improving the operation of the servo systemare substantially the same as are derived in the system of Fig. 2, butit will be observed that the amplifier of Fig. 3 is a balanced pushpullamplifier in which torque, torque rate and torque integral, errorintegral and velocity voltage terms are introduced in a balancedfashion.

Referring now to Fig. 3, one input to the amplifier is represented bythe terminals I33 which are adapted for connection with the output ofeither the azimuth or elevationsensing circuit hereinbefore described.In the present circuit,

this D. C. error signal, derived from the sensing circuit, is appliedacross the terminals I33 which respectively are connected. to thecontrol grids .I45 and I40 and condenser I41.

of tubes I04 and Ill. The signal applied across terminals I03, ofcourse, has a polarity sense depending upon the direction of the azimuthor elevation error and is of a magnitude dependent upon the magnitude ofsaid error. The tubes I04 and I35 in the embodiment illustrated areemployed as cathode followers, the output thereof being derived fromacross cathode resistors I and I01 which are connected in series betweenthe cathodes of the tubes for balanced operation. The output isconnected through conductors I00 and I30 and chokes I40 and I to an RCnetwork indicated generally at I42. The chokes I40 and I together withcondenser I40 serve to filter out frequencies above approximately cyclesper second, and this filter network may, if desired, be omitted.

The network I42 comprises the resistors I44,

supplies signal voltages in its output which are proportional to theactual error or displacement and also error integral. This network alsofunc,-.

tions to attenuate high frequencies with neglig-, ible phase shift. Zerofrequency or D. C. is, of course, passed without attenuation andintermediate frequencies are attenuated increasingly with higherfrequencies but in all cases with a phase shift of less than 90. Theeffect of this network is to cause the system to follow an averagesignal and to eliminate spurious signals of short duration. In otherwords, the response of the servo may be made to cut-oi! at some lowfrequency between /2 and 1% cycles per second and is preferablyaperiodic.

The output of the network I42 is connected across the control grids ofamplifier tubes I40 and I40. The signal voltage output from the manuallycontrolled, signal voltage supplying device 50 which may be of thecharacter hereinabove described is also connected across the controlgrids of tubes I40 and I40 as shown. The manually operated, signalvoltage generator 50 is illustrated as of the type hereinabovedescribed, and corresponding parts thereof bear corresponding referencenumerals. In brief, the signal voltage derived from the potentiometer 11is connected in series with the armature of the permanent magnetgenerator and the resultant voltage is applied through the leads I50 andI5I across the poles of a double-pole, single-throw switch I52, thecontacts of which are connected through leads I50a and I5Ia to theoutput of the RC network I41 above indicated.

For automatic tracking, switch I52 is opened and simultaneously switchI50, hereinafter described, is actuated to move its two arms to thedotted line positions. By opening switch I52 only the error signalderived from the radar sensing circuit is supplied to the amplifier.However, for manual tracking, switch I52 is closed and, due to the lowerimpedance of the manual tracking signal source, or the device 53, ascompared with the impedance of the radar error signal source, it isunnecessary to disconnect the radar error signal source from theamplifier. For example, resistor I44 and I45 would preferably have aresistance of the order of from 500,000 ohms to 2 megohms as comparedwith a maximum resistance value of 10,000 ohms for potentiometer 11.

As herelnbefore indicated, the rate term of the aided tracking controlsignal is provided by potentiometer 11 which is loaded by potentiometer10 to render its output non-linear. The permanent magnet D. C. generator10 serves to provide the displacement signal or aiding tracking por-This network l6 tion of the control voltage. The values of resistanceare so chosen as to provide mainly displacement control or a signal withvery little rate voltage per-unit turn of handwheel for small outputvelocities or where the contact arms of the potentiometers 11 and 10lie'near the midpoints along the lengths thereof. locities, for example,where the wipers of potentiometers 11 and 10 are adjacent an endthereof, the output is predominately a rate control with a large changein the rate signal voltage per unit of a ular movement of the handwheel.It is desirable to provide the above-noted ratio of rate-to-displacementcontrol voltages in order that the tracking device may satisfactorilytrack high speed targets at both long and short ranges The tubes I40 andI40 to which the signal voltages are supplied serve to provide high gainfor the radar error and manual tracking error'signals. If the level ofthe radar signal were to be sumciently high, these tubes could beomitted. The plates of tubes I40 and I4! are respectively resistancecoupled and connected through leads 'I54 and I to the control grids oftubes I00 and I51. The tubes I00 and I01, shown as pentodes, areprovided to control the grids of tubes I00 and I50 in accordance withthe desired control functions and with high voltage gain. The plates oftubes I50 and Ill are connected with the two halves I00 and IOI of thefield winding of generator I02. Condensers I00 and I04 may be connectedacross the respective halves of the field winding of the generatortofilter out undesired A. 0. components. Generator I02 which is similar togenerator I00 hereinabove described has its armature connected incircuit with the armsture of servo motor I05 which has a fixed field asshown and which may be generally similar to the servo motor II2 of Fig.2.

The output of the amplifier controls the direction and strength of thefield of generator I62 and thereby controls the direction and rate ofoperation of servo motor I55. In order to introduce torque terms intothe amplifier and in a predetermined controlling manner, .I connectseries resistors I00, I01, I00 and I00 incircuit between the armaturesof generator I02 and the motor I55. As hereinabove described, the IRdrop across these resistors provides a voltage which is proportional tothe torque exerted by the servo motor I05. When the torque is constant,the,voltage across resistors I10 and "I will respectively besubstantially the same as that across integrating condensers I12 andI10.

Hence, a voltage proportional to motor torque will be supplied in aregenerative fashion across the conductors I54 and I55 and between thecontrol grids I55 and I51. Since this voltage is supplied to theamplifier in a regenerative fashion, loading of the motor will cause arise in armature current and an additional signal to the amplifier,whereby still further to increase the current in the motor generatorcircuit. This, in effect. compensates for varying load conditionswithout requiring a variation in the error signal supplied to theamplifier thereby improving the operation of the servo and rendering itsrate output substantially independent of load or servomotor torqueoutput. The need for this type of control is primarily for tracking atextremely slow speeds, where the motor would tend to stop and start witha varying load and this uneven tracking is mostly noticeable when undermanual control.

As above indicated, condensers I12 and I10 At higher veserve inconnection with the resistors I61, I68, I10 and Ill to supply a signalvoltage in regenerative fashion to the amplifier which is proportionalto a time integration of the torque voltage. Similarly, the condensersI18 and I15 function in connection with the resistors I66, I61, I68 andI69 to supply voltages proportional to a first time derivative of thetorque voltages and to supply these error derivative or rate voltages ina degenerative fashion to the amplifier. The condensers I16 and I15 willalso serve to filter out undesired and spurious voltage components orhigh frequency signals which might otherwise appear on the grids oftubes I56 and I51 and which in some cases might saturate the amplifier.These condensers may serve also to attenuate the servo response forfrequencies above, for example, 4 cycles per second.

As compared to the network I21 of Fig. 2, which provides the signalvoltages which are functions of motor torque, it will be noted that thecorresponding network of Fig. 3 does not combine these signal voltagecomponents in series with the velocity damping voltage derived from therate generator. In the amplifier of Fig. 3, the control voltages whichare functions of the motor torque are supplied to the control grids oftubes I56 and I51 while control voltages which are dependent upon therate of the servo motor output are supplied to the cathodes of thesetubes.

The control voltages which are dependent upon the rate of servo motoroutput are obtained from the permanent magnet generator I16 and networkI11, and the voltage components so derived, being functions of motorspeed, are employed for damping purposes. The servo motor I85 drives thepermanent magnet generator I16, the output of which is connected acrossthe leads I18 and I18. A condenser I86 may be connected thereacross forfiltering purposes. Lead I18 is connected to one contact of a switch I53while the other lead I19 is connected tothe cathode of one of the tubesI56, I51. One of the switch arms of the double-pole, single-throw switchI53 is connected through lead I18a to the cathode of the other of thetubes I56, I51. A condenser II is connected in parallel with resistorI82 and connected between lead I18 and a second contact of the switchI53 which is adapted to be engaged by one of its poles for connectionthrougha resistor I83 with lead I19.

One end of the parallel connected condenser WI and resistor I82 is alsoconnected with a second contact adapted to be engaged by the other ofthe poles of switch I53, so that this end of the parallel circuit willeither be connected to lead I18a or to resistor I83. In one position ofthe switch poles, the parallel connected condenser I8I and resistor I82will be connected in series between leads I18 and HM, while for thesecond position of the switch poles, the parallel connected condenserand resistor will be connected in series with resistor I83 and acrossthe leads I18 and I19.

When the poles of switch I53 occupy the fullline position shown, thepreferred connection will be made for manual control of the servo, whilewhen the switch poles occupy the dotted position, the servo will bearranged for automatic operation. With the switch poles in the firstdescribed position, a signal voltage will be supplied across the cathoderesistors of tubes I56 and I51 which is proportional to the rate of theservo motor or its velocity, and this voltage functions as a velocitydamping factor. At the same 18 time, condenser I8I will be connected inseries with resistor I83 across the leads I18 and I18 and will serve tointegrate the velocity voltage, resistor I83 being preferably arrangedso that the charge developed across the condenser I8I will besubstantially equal to the voltage it would have thereacross if theservo motor I65 were operating under the same speed and under automatictracking conditions.

When the poles of switch I53 are moved to the dotted line position,condenser I8I and resistor I82, which are connected in parallel, will beconnected in series with the armature of generator I16 to provide twodamping factors or a voltage proportional to speed lag and accelerationlag with integration.

The servo motor is controlled in rate and direction of operationinaccordance with the magnitude and polarity or phase sense of the errorsignal supplied to the input of the amplifier, and it is also controlledby the voltages which are proportional to torque, rate of change oftorque and torque integral which are derived and supplied to the controlgrids of the tubes. These signals or control voltages are mixed in thetubes I56 and I51 with the velocity damping voltages and velocityintegral voltages derived from the generator I16 and associated networkI11. Additionally, error voltage integration is achieved in network I82and voltages proportional thereto are additionally supplied to thecontrol grids of tubes I56 and I51.

An electrical servo motor system of the charac ter herein illustratedand described is endowed with highly desirable operating characteristicswhen controlled in the manner above set forth and under the variouscontrol voltages herein described. Additionally, it may be noted thatthe inductance of the field of the generator I62 feeding the servo motoris preferably of such value, for example, henries, that a filteringaction is obtained which causes the output of the generator to beattenuated for frequencies say above about 20 cycles per second, due tothe relatively low plate resistance of the tubes I58 and I59. Thisoperation tends to eliminate jitter of the servo motor at frequencies ofsay from 20 to cycles per second which might otherwise be caused by theD. C. permanent magnet generator I16 feeding back into the amplifierwhen play due, for example, to backlash in the gearing occurs, or whenundesirable phase shifts occur which may be present in some part of theservo loop including the tubes I56 and I51, the output tubes I58 and I59, generator I62, servo motor I65, the gearing or transmission, the D.C. permanent magnet generator I 16 and the RC network connected acrossthe output of the generator I16 and be tween it and the cathoderesistors of tubes I56, I51. Furthermore, stabilization is primarilyprovided, as hereinbefore indicated through the expedient of thevelocity damping and torque rate voltages which are fed back in a,degenerative fashion to the amplifier, and therefore in a manner tooppose fluctuations or changes in the speed and torque of the motor.

It is to be understood that while I have in the foregoing made referenceto resistance-capacitance networks for providing derivative or integralvoltage terms, that I do not wish to be restricted to the use of pureresistances, but that impedances may be employed having resistancecomponents, and furthermore, that the rate-taking circuits may be formedin any desired manner so long as the capacitive reactance of the circuitis large compared with the impedance with which it cooperates inderiving the rate terms. In other words, the present invention is not tobe limited to any particular arrangement or combination of elements forderiving voltages proportional to rate of change or the time integrationof a quantity, and any type of means may be employed for obtaining thesevoltages.

While I have described my invention in its preferred embodiments it isto be understood that the words which I have used are words ofdescription rather than of limitation andthat changes within the purviewof the appended claims may be made without departing from the true scopeand spirit of my invention in its broader aspects.

What is claimed is:

l. A motor control system comprising a motor,

means for controlling the rate and direction of operation of said motorin accordance with a signal voltage, means for producing a voltageproportional to a time integration of the torque developed by saidmotor, and means for supplying said torque integral voltage inregenerativev fashion to said motor control means.

2. A motor control system comprising a motor and generator forcontrolling the rate and direction of operation of said motor, a sourceof control signal for controlling the output of said generator, animpedance connected in series with the armature of said motor and saidgenerator and adapted to have a voltage developed thereacrossproportional to motor torque, integrating means responsive to thevoltage so developed across said impedance supplying a voltageproportional to a time integration of said torque voltage, and means forcontrolling the output of said generator by said control signal and inregenerative fashion by said integration voltage.

3. A motor control system comprising a motor and a generator forcontrolling the speed and direction of operation of said motor, a sourceof control signal for controlling the output of said generator, animpedance connected in series with the armature of said motor and saidgenerator, means for diflerentiating the voltage across said impedance,means for. integrating the voltage across said impedance, and meansresponsive to said control signal and to the integration anddiflerentiation voltage components for controlling the output of saidgenerator.

4. A motor control system comprising a motor and a generator forcontrolling the rate and di-. rection of operation of said motor, asignal source, means for controllin the output of said generator inaccordance with said signal, an impedance connected in series with thearmature of said motor and said generator, a resistance-capacitancenetwork connected to receive the voltage developed across saidimpedance, and circuit means connected with the output of said networkand with said control means for further controlling the output of saidgenerator, said network being so constructed, correlated and arrangedand the component elements thereof being of such values as to supply a,time derivative voltage and an integration voltage across the outputthereof, and

said circuit means being connected to supply said derivative voltage ina degenerative sense and said integration voltage in a regenerativesense to said control means.

5. A motor control system comprising a motor and a generator forcontrolling the rate and direction of operation of said motor, a controlsignal source, an amplifier connected in controllin relation to saidgenerator and adapted to control I the output thereof in response tosaid control signal, an impedance connected in series with the armatureof said motor and with said generator, a resistance-capacitance networkconnected across said impedance, and means connecting the output of saidnetwork with said amplifier, said network being so constructed andarranged and the values of resistance and capacitance therein being suchas to supply voltage outputs proportional to .a time derivative and atime inte ration of the voltage across said impedance, the derivativevoltage across the network output being supplied'to the amplifier in adegenerative sense and the integration voltage component being suppliedto said amplifier in a regenerative sense.

6. A motor control system comprising a motor and a generator for.controlling the rate and direction of operation of said motor, a signalsource, means for controlling the output of said generator in accordancewith said signal, an impedance in series with the armature of saidmotor, a resistance-capacitance network connected to receive the voltagedeveloped across said impedance, and circuit means connected with theoutput of said network and with said control means'for furthercontrolling the output of said generator, the component elements of saidnetwork being of such values as to supply a time derivative voltage andan integration voltage across the output thereof and including a commoncapacitance for supplying both the time derivative and time integralvoltage components, and said circuit means being connected to supplysaid derivative voltage in a degenerative sense and said integrationvoltage in a regenerativ sense to said control means.

7. A motor control system comprising a motor, a signal source, means forcontrolling the rate and direction of operation of said motor inaccordance with said signal, means for producing a voltage proportionalto the torque developed by said motor, resistance-capacitance networksconnected across said voltage-producing means, the components of saidnetworks being of such values as to produce voltage components in theoutputs thereof proportional to time rate of changeof motor torque andto a time integration of motor torque, said diiferentiating andintegrating networks including a common capacitance for supp ing boththe time derivative and time integral voltage components, and a, leadconnecting one side of said capacitance with said motor controllingmeans whereby !urther to control the operation of said motor in aregenerative sense in accordance with torque integral and in adegenerative sense in accordance with rate of change of torque.

8. A motor control system comprising a motor, a generator forcontrolling the speed of said motor, an impedance in series with thearmature of said motor, and differentiating means including adiilerentiating impedance-reactance network connected to receive thevoltage across said impedance for controlling the output of saidgenerator according to the rate of change of the torque of said motor.

9. A motor control system comprising a motor, a generator forcontrolling the speed of said motor, an impedance in series with thearmature of said motor, a diilerentiating impedance-reactance networkconnected across said impedance for producing a voltage corresponding tothe rate of change of the torque of said motor, and a degenerativecircuit connecting the output 01 said 21 difi'erentiating network tocontrol the output of said generator according to the rate of change ofthe torque of said motor.

10. A motor control system comprising a motor, a generator forcontrolling the speed of said motor, an impedance in series with thearmature of said motor, a differentiating impedance-reactance circuitconnected across said impedance for producing a voltage corresponding tothe rate Of change of the torque of said motor, a regenerative feedbackcircuit responsive to the voltage across said impedance for controllingthe output of said generator, and a feedback circuit for supplying theoutput of said differentiating circuit in degenerative fashion tocontrol the output of said generator.

11. A motor control system comprising a motor, a generator forcontrolling the speed of said motor, an impedance in series with thearmature of said motor, means for integrating the voltage developedacross said impedance, a regenerative feedback circuit responsive to theintegration voltage for controlling the output of said generator, aspeed generator driven by said motor for producing a voltagecorresponding to the speed of said motor, and a degenerative circuitresponsive to the voltage of said speed generator for furthercontrolling the output of said firstnamed generator.

12. A motor control system comprising a mo-- tor, a generator forcontrolling the speed of said motor, an impedance in series with thearmature of said motor, an impedance-reactance diiferentiating circuitresponsive to the voltage across said impedance for producing a voltagecorresponding to the rate of change of the torque of said motor, a speedgenerator driven by said motor for producing a voltage corresponding tothe speed of said motor, and a, feedback circuit for controlling saidgenerator in a regenerative sense according to the voltage across saidimpedance and in a degenerative sense according to the output voltagesof said speed generator and said difierentiating circuit.

13. A motor control system comprising a motor, an amplifier having aninput for receiving a signal, a generator responsive to said amplifierfor controlling the speed of said motor according to said signal, animpedance in series with the armature of said motor, means forintegrating the voltage developed across said impedance, and aregenerative circuit for supplying the integration voltage to saidamplifier.

14. A motor control system comprising a motor, an amplifier having aninput for receiving a signal, a generator responsive to said amplifierfor controlling the speed of said motor according to said signal, animpedance in series with the armature of said motor, a differentiatingimpedance-reactance circuit connected across said impedance forproducing a voltage corresponding to the rate of change of the torque ofsaid motor, and a degenerative feedback circuit connecting the output ofsaid differentiating circuit to said amplifier.

15. A motor control system comprising a motor, an amplifier having aninput for receiving a signal, a generator responsive to said amplifierfor controlling the speed of said motor according to said signal, animpedance in series with the armature of said motor, a regenerativefeedback circuit for supplying the voltage across said impedance to saidamplifier, and a differentiating impedance-reactance circuit forobtaining a voltage proportional to the rate of change of the voltageacross said impedance and for supplying it in a degenerative sense tosaid amplifier.

16. A motor control system comprising a motor, means for controlling therate and direction of operation of said motor in accordance with asignal, means for producing a voltage proportional to the torquedeveloped by said motor,

means including an impedance-reactance network connected to receive saidtorque voltage, the impedance and reactance values being such as tosupply a voltage across said impedance proportional to the rate ofchange of torque developed by said motor, and circuit means forsupplying said rate of change of torque voltage in degenerative fashionto control said motor.

17. A motor control system comprising a motor, means for controlling therate and direction of operation of said motor in accordance with asignal, means for producing a signal proportional to the torquedeveloped by said motor, means for integrating said torque signal toprovide a signal proportional to a time integration of the motor torque,and means for controlling said motor in regenerative fashion by saidlast mentioned signal.

18. A motor control system comprising a motor and a generator forcontrolling the rate and direction of operation of said motor, a sourceof control signal for controlling the output of said generator, animpedance connected in series with the armature or said motor and saidgenerator and adapted to have a voltage developed thereacrossproportional to motor torque, means including an impedance-reactancenetwork connected to receive said torque voltage and for supplying avoltage proportional to the rate of change of torque, and means forcontrolling the output of said generator by said control signal and indegenerative fashion by said voltage proportional to rate of change oftorque.

19. A motor control system comprising a motor, means for controlling therate and direction of operation of said motor in accordance with asignal, means for producing a voltage proportional to the torquedeveloped by said motor, means for differentiating said torque voltage,means for integrating said torque voltage, and means for applying thedifferential voltage and the integral voltage in controlling relation tosaid motor controlling means, said differential voltage being applied tosaid control means in a degenerative sense, and said integral voltagebeing applied to said control means in a regenerative sense.

20. A motor control system comprising a motor, a generator forcontrolling the speed of said motor, an impedance in series with thearmature of said motor, an impedance-reactance network connected toreceive the voltage developed across said impedance and for integratingsaid voltage, a regenerative feedback circuit responsive to theintegration voltage for controlling the output of said generator, meansfor producing a voltage corresponding to the speed of said motor, and adegenerative circuit responsive to said speed voltage for furthercontrolling said generator.

21. A motor control system comprising a motor, means for controlling therate and direction of operation of said motor in accordance with acontrol signal, a control signal source connected with said motorcontrol means, means for producing a signal proportional to a timeintegration of the torque developed by said motor, and means forsupplying said torque integral signal in regenerative fashion to saidmotor control means.

amuse 22. A motor control system comprising a motor, means forcontrolling the rate and direction of operation of said motor inaccordance with a control signal, a control signal source connected withsaid motor control means, means for producing a signal proportional tothe torque developed by said motor, means for supplying a signalproportional to a time integration of said torque signal, and means forsupplying said torque signal and said torque integration signal inregenerative fashion to said motor control means.

23. A motor control system comprising a motor, means for controlling therate and direction of operation of said motor in accordance with acontrol signal, a control signal source connected with said motorcontrol means, means for producing a signal proportional to the torquedeveloped by said motor, means for diiferentiating said torque signal,means for integrating said torque signal, and means for supplying thederivative signal and the integral signal in controlling relation tosaid motor controlling means, said derivative signal being applied tosaid motor control means in a degenerative fashion and said integralsignal being supplied to said motor control means in regenerativefashion.

24. A motor control system comprising a motor, means for controlling therate and direction of operation of said motor in accordance with acontrol signal, a control signal source connected with said motorcontrol means, means for producing a signal proportional to the torquedeveloped by said motor, means for supplying a signal proportional to atime derivative and a time integral of 24 said torque signal, means forsupplying said torque signal, torque derivative signal and the torqueintegral signal in controlling relation to said motor control means,said torque signal and torque integral signal being supplied to saidmotor control means in regenerative fashion and said torque derivativesignal being supplied to said motor control means in a degenerativesense.

25. A motor control system comprising a motor and a generator forcontrolling the speed and direction of saidmotor, means for controllingthe output of said generator in accordance with a control signal. asource of control signal connected with said generator control means, animpedance connected in series with the armature oi said motor and saidgenerator for providing a voltage thereacross proportional'to motortorque, means for supplying a voltage proportional to a time integral ofthe voltage across said impedance, and means for supplying said torquevoltage and integral voltage in regenerative fashion to said generatorcontrol means.

. RAWLEY D. McCOY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

